What Marijuana Does To Your Brain And Body

It's 4/20. For those not in the know, "4/20" is the unofficial holiday for pot smokers and marijuana legalization activists around the world to celebrate by lighting up on April 20.

The Huffington Post's Ryan Grim traced the term back to 1971. A group of California high school friends, known as the "Waldos" used "4/20" as a code word to refer to the time of the day when they would smoke outside of school.

The term was popularized in stoner communities, courtesy of the Grateful Dead. It eventually went mainstream, much to the dismay of police, parents, and lawmakers.

Marijuana comes from the cannabis sativa plant, and is the dried and shredded leaves, stems seeds and flowers. The high you get from marijuana comes from a chemical called Tetrahydrocannabinol, also known as THC. Some strains contain more or less THC — making them more or less potent.

Most of THC's effects happen in the brain, where the chemical interacts with receptors on brain cells called cannibinoid receptors. Our bodies actually make chemicals very similar to THC, which are used in normal brain function and development. THC co-opts these natural pathways to produce most of its effects.